In a sauce pan warm the milk, sugar, cream and salt until the sugar is totally dissolved and the cream mixture is steaming, but don't let it boil.

In a separate bowl whisk the egg yolks together. Slowly, while whisking the entire time, pour about a cup of the steaming cream mixture into the egg yolks (called tempering). Whisk the egg mixture back into saucepan with the rest of the cream. Put saucepan back onto the stove and continue whisking until the mixture begins to thicken...they always say "til it coats the back of a spoon," but more importantly do not let it bubble - it will become pudding/custard. I don't know the exact temperature to cook it for, but it takes roughly six minutes on a low heat.

Cool the mixture to room temperature and then add the vanilla bean paste or vanilla extract. Pour into a bowl and cover and refrigerate 8 hours or overnight - I always do overnight.

To make the blackberry swirl, place blackberries, sugar and water in a saucepan and boil. Continue boiling until the blackberries break down and the liquid becomes a thick syrup. This will take about 12 minutes, roughly. Put this in the fridge too - it is imperative this is totally chilled and cold when you mix with the ice cream.